Numerous studies have investigated motor learning by examining the adaptation
of reaching movements to visuomotor perturbations that alter the mapping between actual
and visually perceived hand position. The picture of the visuomotor transformation from
visual input to motor input that has developed consists of three broad phases: integration
of hand and target locations in a common reference frame, calculation of a movement
vector between hand and target, and transformation of this movement vector from the
common reference frame into motor commands. The process of adapting to a visuomotor
rotation is generally viewed as an alteration of the vectorial representation of reach
planning. When visual feedback is rotated, the motor and visual directions no longer
coincide and the motor command executed is remapped to the subsequent visual direction
produced. In the current set of studies, we examined how learning a visuomotor rotation
while reaching to a target with a curved hand path generalizes to straight path reaching
and novel target directions. We found that there is very little to no generalization of
learning between curved reaches and straight reaches when given only endpoint
feedback. With continuous visual feedback, we found partial transfer. This suggests that
in the absence of visual feedback, the vectorial adaptation hypothesis is insufficient and
adaptation to a visuomotor rotation is mediated by the later stages of the visuomotor
transformation, when the motor commands specific to the hand path used are being
generated.